It is standard to provide a mixing valve used in a bathtub with a diverter valve so that the output of the mixing valve can be fed either to the faucet or to the shower. Such a valve is normally set up so that, if set to divert flow to the shower, once the pressure is relieved it resets to divert flow to the faucet.
The standard such valve assembly as described in German patent document 4,323,496 of W. Gnauert. it has a valve housing formed with a bore open at a surface and extending along an axis, an inlet passage opening into the bore, inner and outer outlet passages also opening into the bore, and an inner valve seat between the inlet passage and the inner outlet passage. The inlet passage is itself supplied with water from a mixing valve connected to hot- and cold-water lines. A sleeve fitted in the bore forms an outer valve seat between the inlet passage and the outer outlet passage. A valve body is displaceable in the bore between an inner position against the inner seat and blocking flow from the inlet passage to the inner outlet passage and an outer position against the outer seat and blocking flow from the inlet passage to the outer outlet passage. Normally a faucet is connected to one of the outlet passages and a shower to the other.
This structure is fairly bulky and unattractive. The complex diverter valve projects from the valve housing considerably. Furthermore mounting the diverter-valve parts on the main valve is fairly complex.